Advances in the field of biotechnology have led to significant advances in the treatment of diseases such as cancer, genetic diseases, arthritis and AIDS that were previously difficult to treat. Many such advances involve the administration of oligonucleotides and other nucleic acids to a subject, particularly a human subject. The administration of such molecules via parenteral routes has been shown to be effective for the treatment of diseases and/or disorders. See, e.g., Draper et al., U.S. Pat. No. 5,595,978, Jan. 21, 1997, which discloses intravitreal injection as a means for the direct delivery of antisense oligonucleotides to the vitreous humor of the mammalian eye. See also, Robertson, Nature Biotechnology, 1997, 15, 209, and Genetic Engineering News, 1997, 15, 1, each of which discuss the treatment of Crohn's disease via intravenous infusions of antisense oligonucleotides. Non-parenteral routes for administration of oligonucleotides and other nucleic acids (such as oral or rectal delivery or other mucosal routes) offers the promise of simpler, easier and less injurious administration of such nucleic acids without the need for sterile procedures and their concomitant expenses, e.g., hospitalization and/or physician fees. There thus is a need to provide compositions and methods to enhance the availability of novel drugs such as oligonucleotides when administered via non-parenteral routes. It is desirable that such new compositions and methods provide for the simple, convenient, practical and optimal non-parenteral delivery of oligonucleotides and other nucleic acids.